The present invention relates to a process for the manufacture of Optically Active .gamma.-lactone of (1R,Cis)-2, 2-Dimethyl-3-hydroxymethyl Cyclopropane-1-Carboxylic Acid (hereinafter referred to as Optically active (1R, Cis)-.gamma.-lactone or optically active .gamma.-lactone) and more particularly to the synthesis of the optically active .gamma.-lactone from optically active Car-3-en-5-one.
Optically inactive .gamma.-lactone of Cis-2,2-dimethyl-3-hydroxymethyl cyclopropane carboxylic acid, having the following formula I ##STR1## is a known compound and is manufactured by a multi-step process. Besides, this is a very well known intermediate for the manufacture of optically inactive Cis-methyl-2, 2-dimethyl-3-formyl cyclopropane carboxylate of the formula II, a valuable intermediate for the synthesis of optically inactive Cis-Chrysanthemic acid of the formula III, A-Krief et.al., Tet. Lett. 3915(1976) and Pyrethroid acid of formula IV, J. Martel et al., DOS2827627 (1979), Roussel-Uclaf. Formulae II, III and IV are shown below ##STR2## The importance of optically active .gamma.-lactone is that it is a convenient starting material for the manufacture of optically active (1R, Cis)-Pyrethroid acid of formula IV which latter in turn could be converted to optically active (1R, Cis)-Synthetic Pyrethroid such as formula V and VI which correspond to the structure of formula III where in formula V,X=Cl and ##STR3## and in formula VI,X=Cl or Br and ##STR4## It is also established that the above optically active (1R, Cis)-Synthetic Pyrethroid possesses much more insecticidal activity than the corresponding optically inactive compounds. There is only one report available in the prior art wherein the said optically active .alpha.-lactone is synthesized from (+)-3-Carene in seven steps, see U.S. Pat. No. 4,219,562.